Antenna diversity radio receiving arrangement for telecommunications systems using block-oriented transmission of radio messages

ABSTRACT

In an antenna diversity base station of a DECT cordless telephone, at least one antenna change is carried out, for example on the basis of field strength measurements (FSM1, FSM2), in order to improve the “antenna diversity” during the reception of a DECT radio message, for example of a synchronization initiation word (E-SEW) of a synchronization field (SYF) to the DECT standard. As a result of the fact that the antenna change takes place during the reception of the synchronization initiation word (E-SEW), both optimum “antenna diversity” and interference-free transmission of wanted information contained in the radio message are possible in each transmission time slot of the DECT radio message.

BACKGROUND OF THE INVENTION

The invention relates to an antenna diversity radio receivingarrangement for telecommunications systems using block-orientedtransmission of radio messages.

Telecommunications systems using block-oriented transmission of radiomessages are being technically developed, linked to various standards,analogous to the ISDN Standard (Integrated Services Digital Network)which has already been in existence for a relatively long time incable-based telecommunications technology. The term “block-orientedtransmission” essentially defines methods of transmitting radio messageswhich are transmitted using the time division multiple access method(TDMA=Time Division Multiple Access) or using the code division multipleaccess method (CDMA=Code Division Multiple Access). Knowntelecommunications systems, based on the TDMA method, are, for example,cordless telecommunications systems to the DECT Standard (DigitalEuropean Cordless Telecommunication) and mobile radio telecommunicationssystems to the GSM Standard (Global Systems for Mobile Communication).

A dynamic channel selection from about 120 available channels is carriedout for cordless telecomunication to the DECT Standard (cf. EuropeanTelecommunication Standard -Final Draft-; prETS 300 175-1, 5/1992;ETS-Institute 06921 Sophia Antipolis, France). The 120 channels resultfrom the fact that ten frequency bands between 1.8 and 1.9 GHz are usedin the DECT Standard, a time division multiple access frame of 10 msbeing used in the time division multiple access mode (TDMA=Time DivisionMultiple Access) in each frequency band, as illustrated in FIG. 1. 24(from 0 to 23) time channels are defined in this time division multipleaccess frame and thus govern a frame layout. This frame layout is thenused in such a manner that a maximum of 12 mobile sections PT (PortableTermination), which are assigned to a base station FT (FixedTermination), of a DECT telecommunications system can operatesimultaneously in the duplex mode (PT→FT and FT→PT as well as FT→PT andPT→FT) for each frequency band.

In this case, the 24 time channels are in each case assigned time slotshaving a time slot duration of 417 μs. The time slot in this caseindicates the time in which information (data) is transmitted. Thistransmission of information in the duplex mode is also called the pingpong method since transmission is carried out at a specific time andreception is carried out at a different time. In this ping pong method,a burst having a time duration of 365 μs or a bit length of 420 bitswith a data throughput of 42 kBit/s is transmitted in each time slot.Taking account of the fact that 30 bits are in each case available in asecurity time frame GS (Guard Space) at both ends of the time frame inorder to avoid adjacent time slots overlapping, this results in a totaldata throughput of 1.152 MBit/s with respect to the time divisionmultiple access frame. The chronological sequence of the transmittedpulses per time division multiple access frame defines, according toFIG. 2, a PH channel, the so-called physical channel, which is assignedto a so-called physical layer (PH-L). The data package of 420 bitstransmitted in this case is called a PH package and is assigned to a Dfield. Of the 420 data bits (sequence of H/L bit values) in the PHpacket, 32 bits are used for synchronization to a synchronization fieldSYF, and 388 bits are used for the transmission of wanted information toa wanted information field NIF.

The 32 bits in the synchronization field SYF are in turn divided intotwo data bit sequences of 16 bits each. The first data bit sequence(sequence with the first 16 H/L bit values) is a synchronizationinitiation word SEW, which is used to initiate synchronization. For atransmission direction “mobile section PT→base station FT”, thissynchronization initiation word SEW ideally comprises a periodic “101”or “TLH” sequence, and a likewise periodic “010” or “LEHL” sequence forthe opposite transmission direction “base station FT→mobile section PT”.The base station/mobile section assignments shown in brackets in FIGS. 1and 2 are possible as alternatives depending on which sequence isassigned to which transmission direction.

The second data bit sequence (sequence with the second 16 H/L bitvalues) is a synchronization confirmation word SBW which must be used toconfirm the synchronization initiated using the synchronizationinitiation word SEW. Essentially, the data bits of the synchronizationconfirmation word SBW must be identified with this confirmation. Only ifthis is the case is the synchronization initiated using thesynchronization initiation word SEW accepted. The synchronization is inthis case initiated if it is possible to assume, with a certainprobability, that the synchronization initiation word SEW is an “HLH” or“LHL” sequence.

Furthermore, other layers are also defined in the DECT Standard,analogous to the ISDN Standard using the ISO/OSI 7-layer model. One ofthese layers is a medium access control layer (MAC-L) to which,according to FIG. 3, the 388 bits in the wanted information field NIFare assigned for transmission of wanted information. The wantedinformation field NIF is in this case composed of an A field and a Bfield. The A field comprises 64 bits of the 388 bits in the wantedinformation field NIF and these are used, inter alia, for messages whenthe base station is connected to the mobile sections of the DECTtelecommunications system. The other 324 bits are assigned to the Bfield, 320 bits thereof being used for voice data and 4 bits to identifypartial interference of the pulse. Finally, the 324 bits in the B fieldare assigned to other ISO/OSI layers in the context of the ISO/OSI7-layer model.

In the simplest form, the DECT telecommunications system has a basestation with at least one mobile section. More complex (for examplenetwork) systems contain a plurality of base stations, each having aplurality of mobile sections. On the basis of the 24 time channelsdefined in the DECT Standard, up to 12 mobile sections can be assignedto the base station, which communicate with the base station using theduplex mode. For the time division multiple access frame, which islikewise defined in the DECT Standard, of 10 ms, the duplex mode meansthat information is transmitted from the base station to the mobilesection, or vice versa, every 5 ms.

When transmitting radio-frequency-modulated radio messages—for exampleDECT radio messages in the GHz band—, the transmission conditionsfrequently differ very considerably within a small physical region of afew centimeters (centimetric region) because of the propagationcharacteristics of the radio-frequency carrier signal. In the case ofmobile systems, such as the DECT telecommunications system, this resultsin the transmission conditions fluctuating greatly with time even at lowspeeds of about 1 m/s. In order to counter at least partially these timefluctuations in the transmission conditions, it is known for a second,physically offset antenna to be installed at least at one part of themobile system (for example the base station). Because of the physicalseparation, the reception conditions at the antennas differ and can beselected by antenna switching. This method, which is known by the term“antenna diversity” (cf. Proceedings of International Conference onCommunications—ICC'91; Jun. 23-26, 1991, New York (US), pages 1480 to1484 and Patent Abstracts of Japan, Vol. 11, No. 231 (E-527), Jul. 28,1987 in conjunction with JP-A-62047222) enables improved reception ofradio messages in mobile systems when the transmission conditions arepoor in places. The antenna diversity method is suitable in particularfor DECT telecommunications systems based on the TDMA method, in thecase of which it is possible to change the antenna in the time betweentwo time slots without this interfering with the transmitted radiomessage.

If, according to FIGS. 4 and 5, at least two antennas A1, A2 but onlyone receiver REC, which is assigned to a radio section RE, RE-T, RE-R ofthe antenna diversity radio receiving arrangement FT, PT, are used in anantenna diversity radio receiving arrangement FT, PT which is known fromWO 94/10812 (for example a base station and/or mobile section of acordless telephone), then, according to WO 94/10764, there is a criticalproblem in the control of the antenna diversity switching in that thereception conditions cannot be assessed simultaneously at the twoantennas. It is therefore proposed that the reception conditions bechecked once per time slot, for example by a field strength measurementand/or evaluation of transmission errors (CRC errors: Cycle RedundancyCheck). These current and preceding checks, which are related to timeslots, are used to decide whether the radio message transmitted In thesubsequent time slot will be received on the same antenna or on adifferent antenna. However, since the transmission conditions can changeseverely in the time between two time slots, this known antennadiversity method does not guarantee that the chosen antenna offers thebest possible reception at this time.

Furthermore, U.S. Pat. No. 5,241,701 discloses an antenna diversityradio receiving arrangement for telecommunications systems usingblock-oriented transmission of radio messages, in which the antennadiversity means assigned to the radio receiving arrangement and havingtwo antennas assigned thereto are designed in such a manner that, duringthe receiving of time duration a message block (time slot) of the radiomessage, at least two different antennas, which are assigned to theantenna diversity means, are assigned alternately to the receivingchannel of the antenna diversity radio receiving arrangement, as thereceiving antenna.

SUMMARY OF THE INVENTION

International application WO 94/08404 or, respectively, U.S. Pat. No.5,369,801 discloses an antenna diversity radio reception arrangement fortelecommunication systems with a block-oriented transmission of radiomessages or, respectively, an antenna selection method in an antennadiversity radio reception arrangement for telecommunication systems witha block-oriented transmission of radio messages wherein or,respectively, whereby the antenna selection occurs during the receptionof synchronization bits (“MUX 2” format) exhibiting redundant data(bits) or of useful information bits configured as “low significantbits” (“MUX 1” format).

The object underlying the invention is comprised in specifying anantenna diversity radio reception arrangement for telecommunicationsystems with a block-oriented transmission of radio messages that,compared to known arrangements, also enables a reliable “antennadiversity” when the synchronization bits known from the prior art duringwhose reception the antenna selection occurs comprise no redundant data(bits).

The object underlying the invention is also comprised in specifying anantenna selection method in an antenna diversity radio receptionarrangement for telecommunication systems with a block-orientedtransmission of radio messages that, compared to known methods, alsoenables a reliable “antenna diversity” when the synchronization bitsknown from the prior art during whose reception the antenna selectionoccurs comprise no redundant data (bits).

In an antenna diversity radio reception arrangement fortelecommunication systems with a block-oriented transmission of radiomessages (for example an antenna diversity base station of a DECTcordless telephone, or, respectively, given an antenna selection methodin an antenna diversity radio reception arrangement fortelecommunication systems with a block-oriented transmission of radiomessages, for example an antenna diversity base station of a DECTcordless telephone) at least one antenna change is undertaken (forexample on the basis of field strength measurements) during thereception of a synchronization preamble word that contains redundantdata and belongs to a synchronization field contained in a message blockof a radio message (for example a DECT radio message) and composed ofthe synchronization preamble word and a synchronization confirmationword. It is undertaken for the improvement of the “antenna diversity” inthe sense of the object underlying the invention. In that the antennachange ensues during the reception of the synchronization preamble word,both an optimum “antenna diversity” as well as a disturbance-freetransmission of useful data contained in the radio message are possiblein every transmission time slot of the DECT radio message.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention which are believed to be novel,are set forth with particularity in the appended claims. The invention,together with further objects and advantages, may best be understood byreference to the following description taken in conjunction with theaccompanying drawings, in the several Figures of which like referencenumerals identify like elements, and in which:

FIGS. 1-5 depict prior art antenna diversity radio receivingarrangements.

FIG. 6 shows a reception synchronization field of the base station whichis subject to interference as a result of an antenna change, in the caseof an antenna diversity base station of a DECT cordless telephone,

FIG. 7 shows the chronological sequence of a plurality of DECT burstsoccurring in the DECT time division multiple access frame.

FIG. 8 depicts an antenna selection means for carrying out the antennachange using a plurality of series-connected counters whichsubstantially produce the antenna diversity control signals with respectto the synchronization signal.

FIG. 9 depicts an antenna selection means according to FIG. 8, whereinthe individual counters relating to the mobile stations are connected toa further OR gate.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 6 shows a reception synchronization field E-SYF which is receivedby an antenna diversity base station of a DECT cordless. telephone, hasa synchronization initiation word E-SEW at the receiving end and has asynchronization confirmation word E-SBW at the receiving end, as ananalog signal which is interfered with as a result of at least oneantenna change at the antenna diversity base station. The receptionsynchronization field E-SYF is in this case the image of a transmissionsynchronization field which is transmitted, for example, by a mobilesection of the DECT cordless telephone, is transmitted on the radio pathbetween the mobile section and the base station and has asynchronization initiation word at the transmission end and asynchronization confirmation word at the transmission end. Thetransmission synchronization field, which is 32 bits long according tothe illustration in FIG. 2, is transmitted immediately after theactivation of the mobile section. For the data rate of 1.152 Mbit/sstated initially, about 27.8 μs are required for the transmissionmission (sending and receiving) of the transmission and of the receptionsynchronization field. Of this, 13.9 μs are required for thetransmission of the synchronization initiation word, and 13.9 μs arelikewise required for the transmission of the synchronizationconfirmation word.

While the synchronization initiation word E-SEW at the receiving end isused to synchronize the antenna diversity base station at bit level, thesynchronization confirmation word E-SBW at the receiving end is used tosynchronize the antenna diversity base station at word level. Since thesynchronization initiation word at the transmission end is assignedsynchronization information, which comprises an alternating “1/0” or“0/1” bit sequence, and since all that is required for bitsynchronization is to identify the “1/0”, or “0/1” alternation in thebit sequence, the synchronization information contained in thesynchronization initiation word E-SEW at the receiving end—forinterference-free transmission on the radio path—has a redundantinformation element. As a result of this redundancy in thesynchronization information, the synchronization initiation word E-SEWat the receiving end is available as a time period for one or moreantenna changes at the antenna diversity base station, for improved“antenna diversity”. Therefore, the synchronization initiation wordE-SEW at the receiving end is suitable for this purpose, since

(1) the choice of antenna should be complete at the time of reception ofthe synchronization confirmation word E-SBW at the receiving end, sincecorrect identification of the synchronization confirmation word E-SBW atthe receiving end is critical to reception or loss of the informationtransmitted in the time slot, and

(2) interference in one or a few bits in the 16-bit long synchronizationinitiation word E-SEW is not relevant since, from experience, even a fewbits (approximately 6 bits) are sufficient to achieve bit synchronism.

The individual method steps which take place in the base station inorder to carry out the antenna change, for example from a first antennaA1 to a second antenna A2, will be explained in the following text withreference to FIG. 6. For the present exemplary embodiment, theindividual method steps are in this case preferably carried out every 10μs in the time slots in which the mobile section is transmitting and thebase station is receiving. This situation does not change at all evenwhen, in the opposite case, the mobile section, or even both the mobilesection and the base station, have at least two antennas and the basestation is in this case transmitting while the mobile section isreceiving. For this transmission/reception direction, the correspondingreception synchronization field would then—according to FIG. 2—have abit sequence which is inverted with respect to the receptionsynchronization field E-SYF according to FIG. 6.

At a time t1, at which the antenna A1 is being used as a receivingantenna, a first field strength measurement FSM1 is started by a firstantenna diversity control signal SS1 of the base station. Themeasurement in this case extends, for example, over a first measurementtime period τ1, in which, for example, four bits (the 2nd bit to the 5thbit of the synchronization initiation word E-SEW at the receiving end)have already been evaluated for bit synchronization. Subsequently, at asecond time t2, an antenna change from the first antenna A1 to thesecond antenna A2 is initiated by a second antenna diversity controlsignal SS2 of the base station. This antenna change is completed,because of a switching-dependent changeover time (cf. FIG. 8), at a timet2′. The initiation of the antenna change at the time t2 takes place,for example, during the sixth bit (a low bit according to FIG. 6) in thesynchronization initiation word E-SEW at the receiving end. Therespective bit may in this case be interfered with by the antennachange. This interference is represented in FIG. 6 by a firstinterference pulse SI1. After the antenna change, a second fieldstrength measurement FSM2 is started at a time t3 at the antenna A2 ofthe base station by a second antenna diversity control signal SS3. Thissecond measurement FSM2 in this case extends over a second measurementtime period τ2, whose duration for measurement purposes corresponds,however, to that of the first measurement time period τ1. If required, afurther four bits (the 8th bit to the 11th bit of the synchronizationinitiation word E-SEW at the receiving end) have been evaluated for bitsynchronization in the measurement time period τ2. In order that thesame ratio of low bits (“0” bits) to high bits (“1” bit) is measured inboth measurement time periods, the starting times t1, t3 for the fieldstrength measurements FSM1, FSM2 are separated in time by an evenmultiple of the bit transmission time. For the DECT cordless telephone,this bit transmission time is about 868 ns. The time relationshipbetween the starting times t1, t3 is therefore important, because thefirst antenna diversity control signal SS1 can be generated only withlimited accuracy. The reasons for this will be explained in thefollowing text with reference to FIG. 7.

FIG. 7 shows the chronological sequence, related to time slots, of aplurality of reception bursts EB1, EB2, EB3, which are received by thebase station of the DECT cordless telephone in a plurality of timedivision multiple access frames and originate from correspondingtransmission bursts transmitted by the mobile section of the DECTcordless telephone. In the active connection state (communication state)between a radio transmitting arrangement (in this case: mobile sectionof the DECT cordless telephone) and a radio receiving arrangement (inthis case: base station of the DECT cordless telephone), a burst with alength of about 365 μs is transmitted in time slots every 10 ms inaccordance with the statements relating to FIG. 1. During the time inwhich there is no connection and which has a time duration of about 9635μs (quiescent state), the clock frequencies emitted by correspondingtimers in the mobile section and the base station can drift in time withrespect to one another by a maximum of ⅓ bit. For a bit transmissiontime of 868 ns, this time drift corresponds to a time interval of 260.4ns.

Because of this time drift, which is specific to cordless telephones,the first antenna diversity control signal SS1 can also be generatedonly with a time uncertainty of 260.4 ns with respect to a referencesignal. A synchronization signal SDS, which is called Sync DetectSignal, is available, for example as the reference signal in this case,which synchronization signal SDS occurs regularly in each time slot witha time error of 0.264 μs and by means of which the time slot-relatedsynchronization is initiated. The time interval between the timeslot-related synchronization signal SDS and the start of the next timeslot is about 9973 μs. This time interval of 9973 μs is used as the timereference variable for the measures which are required in conjunctionwith the “antenna diversity” to be improved. Thus, for example, if thebase station has received an n-th reception burst in an n-th (forexample the first, where n=1) time slot with an n-th synchronizationsignal as the reference signal for the antenna diversity control signalSS1, the time t1 for the first field strength measurement FSM1 occurs9973 μs later in an (n+1)-th (second) time slot.

Defining the time t1 in this way also unambiguously defines the timest2, t3. This also applies in the same way to other times t4, t5, t5′according to FIG. 6 which are related to the improvement of the “antennadiversity”.

Until a fourth time t4, the field strength readings resulting from thetwo field strength measurements FSM1, FSM2 are compared and a comparisonresult is defined as a function of them. If a fourth antenna diversitycontrol signal SS4 confirms on the basis of the comparison result thatthe second reading resulting from the second field strength measurementFSM2 is less than the first reading resulting from the first fieldstrength measurement FSM1, then the system switches back to the antennaA1 (repeated antenna change) at a fifth time t5. This antenna change iscomplete at a time t5′. As a result of the start of the antenna changeat the time t5, for example during the twelfth bit (a low bit accordingto FIG. 6) in the synchronization initiation word B-SEW at the receivingend, a second interference pulse SI2 is produced, which can interferewith the corresponding bit. The two interference pulses SI1, SI2 whichare caused by the respective antenna change in general have no directeffect on the identification of the “1/0” or “0/1” alternation in thebit sequence in the synchronization initiation word E-SEW at thereceiving end. It can therefore be assumed, with a certain probability,that

(1) the alternation in the bit sequence can be identified even withoutthe two bits which are subject to interference, and

(2) if the alternation in the bit sequence is not identified, there isalso a certain probability of these bits together with the two bitswhich are possibly not subject to interference being identified, andloss of the reception burst would thus have been prevented.

FIG. 8 shows antenna selection means AAM by means of which the methodsteps for carrying out the antenna change, which are described in FIG.6, can be carried out. The antenna selection means AAM according to theillustration in FIG. 8 preferably comprises an arrangement of electroniccircuits. This antenna selection means AAM or circuit arrangement isassigned to antenna diversity means RE, RE-T, RE-R, DS, RSSI, A/D, M-CTof the antenna diversity radio transmitting arrangement and radioreceiving arrangement FT, PT according to FIGS. 4 and 5. As analternative to the electronic circuit arrangement, the antenna selectionmeans may also be formed as program modules, provided it is possibleusing these means to determine quickly enough the antenna selectioncriterion—the field strength in the present exemplary embodiment. Theidentification/non-identification of a TDMA-specific signal sequence inthe radio message (in this case: the “1/0” signal sequence in thesynchronization initiation word E-SEW at the receiving end) could beused, for example, as a further selection criterion.

The antenna selection means AAM has a plurality of series-connectedcounters Z1 . . . Z4 which essentially produce the antenna diversitycontrol signals SS1 . . . SS4 with respect to the synchronization signalSSD (Sync Detect Signal). The use of counters is possible in particularbecause all the time intervals which result from the time differencesbetween the times t1. . . t5′ and a time t0 (when the synchronizationsignal SSD occurs) can be derived from the bit clock rate of 1.152 MHz.A first counter Z1 is controlled on the input side at the time to by thesynchronization signal SSD.

By counting cime units which correspond to the bit clock rate, thecounter Z1 in this case detects a first time interval δt1, which isobtained from the time interval between the times t1, t0. This timeinterval δt1 is—according to the statements relating to FIGS. 6 and7—9973 μs. After the detection of the time interval δt1, the counter Z1emits the first antenna diversity control signal SS1 at the time t1 tothe input of a second counter Z2 and to a control input of a firstintegrator INT1. The second counter Z2 and the first integrator INT1 areactivated by the first control signal SS1.

By counting time units which correspond to the bit clock rate, thesecond counter Z2 in this case detects a second time interval δt2, whichis obtained from the time interval between the times t2, t1. In thepresent exemplary embodiment, this time interval δt2is about 3.5 μs.During this time interval δt2, which corresponds to the measurement timeperiod τ1, the first field strength measurement FSM1 is carried out atthe integrator INT1. During this measurement, first field strengthvalues RSSV1 (Radio Signal Strength Values), which are supplied on theinput side to the integrator INT1 during the measurement time period τ1,are integrated to form a first output signal AS1.

After the second time interval at2 and the measurement time period τ1have elapsed, the second antenna diversity control signal SS2 issupplied at the time t2 on the input side to a third counter Z3 and to aan OR gate GT1. An OR logic signal VKS1 is produced at the gate GT1 bythe control signal SS2, and the antenna change from the first antenna A1to the second antenna A2 takes place as a result of this signal at thetime t2′ (governed by the gate delay time at the OR gate GT1).Furthermore, the third counter Z3 is activated by the control signal SS2so that, by counting time units which correspond to the bit clock rate,this third counter Z3 detects a third time interval δt3. This timeinterval δt3, which indicates the time interval between the times t3,t2, is 1.7 μs in the present exemplary embodiment.

After detecting this time interval δt3, the third antenna diversitycontrol signal SS3 is produced by the third counter Z3 at the time t3,is supplied on the input side to a fourth counter Z4 and is passed to acontrol input of a second integrator INT2. The counter Z4 and theintegrator INT2 are activated by the control signal SS3. Followingactivation, by counting time units which correspond to the bit clockrate, the counter Z4 detects a fourth time interval δt4, which isobtained from the time interval between the times t4, t3. Like the timeinterval δt2, the time interval δt4 is 3.5 μs long. The time intervalδt4 corresponds, furthermore, to the second measurement time period τ2illustrated in FIG. 6. In this measurement time period τ2, second fieldstrength values RSSV2 which are applied to the input of the integratorINT2 are integrated to form a second output signal AS2.

At the time t4, the fourth counter Z4 emits a fourth antenna diversitycontrol signal SS4 to an AND gate GT2. In addition, until this time t4,a comparison is carried out between the two output signals AS1, AS2. Todo this, these output signals are supplied to a comparator KOM whichproduces a comparison signal VS from these two output signals AS1, AS2.This comparison signal VS is likewise supplied to the AND gate GT2. TheAND gate GT2 forms an AND logic signal VKS2 from the control signal SS4and the comparison signal VS, which AND logic signal VKS2 is supplied ata time t4′ (governed by the gate delay time at the AND gate GT2) to theOR gate GT1. The control signal SS2 and the AND logic signal VKS2 arelogically combined in the OR gate GT1. The OR logic signal VKS1 producedin the process results in the system switching back from the secondantenna A2 to the first antenna A1 at the time T5, irrespective of thecontrol signal SS2, because the field strength measurements FSM1, FSM2have shown that the reception on the first antenna A1 is better thanthat on the second antenna A2.

Since a DECT base station operates simultaneously with a plurality ofmobile sections (up to 12 mobile sections which all drift differently tothe base station with respect to time), the complexity for generatingthe first antenna diversity control signal SS1 increases in such amanner that a dedicated first counter has to be provided for eachindividual mobile section. An appropriate design of the antennaselection means for this purpose is shown on the basis of FIG. 8 andFIG. 9, where the individual counters Z1.1 . . . Z1.12 relating to themobile section are connected on the output side, for example, to afurther OR gate GT3.

The invention is not limited to the particular details of the apparatusdepicted and other modifications and applications are contemplated.Certain other changes may be made in the above described apparatuswithout departing from the true spirit and scope of the invention hereininvolved. It is intended, therefore, that the subject matter in theabove depiction shall be interpreted as illustrative and not in alimiting sense.

What is claimed is:
 1. An antenna diversity radio receiving arrangementfor telecommunications systems using block-oriented transmission ofradio messages, comprising: antenna diversity system having a pluralityof antennas, the plurality of antennas being structured such that a) atleast two different antennas of the plurality of antennas allocated tothe antenna diversity system are allocated in alternation to a receptionchannel of the antenna diversity radio receiving arrangement asreception antenna during a reception time span of a synchronizationpreamble word that contains redundant data and belongs to asynchronization field contained in a message block of the radio messageand that is composed of the synchronization preamble word and asynchronization confirmation word; b) of the plurality of antennasallocated to the reception channel during the reception time span of thesynchronization preamble word; an antenna having a best receptioncharacteristic for the reception time span of the message block isallocated to the reception channel.
 2. The antenna diversity radioreceiving device as claimed in claim 1 wherein the radio message is aTDMA radio message.
 3. The antenna diversity radio receiving device asclaimed in claim 1 wherein the radio message is a CDMA radio message. 4.The antenna diversity radio receiving device as claim in claim 1,wherein the antenna diversity system has a antenna selection devicewhich is structured such that antenna selection is carried out by fieldstrength measurements.
 5. The antenna diversity radio receiving deviceas claimed in claim 4, wherein the antenna selection device has acomparator to which voltage values corresponding to measured fieldstrength values of the field strength are supplied.
 6. The antennadiversity radio receiving device as claimed in claim 2, wherein theantenna selection system is structured such that antenna selection iscarried out by identification/non-identification of a TDMA-specificsignal sequence in the radio message.
 7. The antenna diversity radioreceiving device as claimed in claim 6, wherein the TDMA-specific signalsequence is a “1/0” signal sequence.
 8. The antenna diversity radioreceiving device as claimed in claim 4, wherein the antenna selectionsystem is structured such that antenna selection is carried out byidentification/non-identification of a TDMA-specific signal sequence inthe radio message.
 9. The antenna diversity radio receiving device asclaimed in claim 8, wherein the TDMA-specific signal sequence is a “1/0”signal sequence.
 10. A method for selecting antennas in an antennadiversity radio receiving arrangement for telecommunication systemsusing block-oriented transmission of radio messages, comprising thesteps of: a) allocating at least two different antennas in alternationto a reception channel of the antenna diversity radio receivingarrangement as reception antenna during a reception time span of asynchronization preamble word that contains redundant data and belongsto a synchronization field contained in a message block of a radiomessage and composed of the synchronization preamble word and asynchronization confirmation word; b) allocating to the receptionchannel an antenna of the at least two different antennas, allocated tothe reception channel during the reception time span of thesynchronization preamble word, having a best reception characteristicfor the reception time span of the message block.
 11. The antennadiversity radio receiving device as claimed in claim 2, wherein themessage block is a DECT-specific message block.
 12. The antennadiversity radio receiving device as claimed in claim 4, wherein themessage block is a DECT-specific message block.